The diagnosis and/or treatment of disease in nuclear medicine constitute one of the major applications of short-lived radioisotopes. It is estimated that in nuclear medicine over 90% of the diagnostic procedures performed worldwide annually use 99mTc labelled radio-pharmaceuticals. Given the short half-life of radio-pharmaceuticals, it is helpful to have the facility to generate suitable radioisotopes on site. Accordingly, the adoption of portable hospital/clinic size 99mTc generators has greatly increased over the years. Portable radioisotope generators are used to obtain a shorter-lived daughter radioisotope which is the product of radioactive decay of a longer-lived parent radioisotope, usually adsorbed on a bed in an ion exchange column. Conventionally, the radioisotope generator includes shielding around the ion exchange column containing the parent radioisotope along with means for eluting the daughter radioisotope from the column with an eluate, such as saline solution. In use, the eluate is passed through the ion exchange column and the daughter radioisotope is collected in solution with the eluate, to be used as required.
In the case of 99mTc, this radioisotope is the principle product of the radioactive decay of 99Mo. Within the generator, conventionally the 99Mo is adsorbed on a bed of aluminium oxide and decays to generate 99mTc. As the 99mTc has a relatively short half-life it establishes a transient equilibrium within the ion exchange column after approximately twenty-four hours. Accordingly, the 99mTc can be eluted daily from the ion exchange column by flushing a solution of chloride ions, i.e. sterile saline solution through the ion exchange column. This prompts an ion exchange reaction, in which the chloride ions displace 99mTc but not 99Mo.
In the case of radio-pharmaceuticals, it is highly desirable for the radioisotope generation process to be performed under aseptic conditions i.e. there should be no ingress of bacteria into the generator. Moreover, due to the fact that the isotope used in the ion exchange column of the generator is radioactive, and is thereby extremely hazardous if not handled in the correct manner, the radioisotope generation process also should be performed under radiologically safe conditions. Therefore, current radioisotope generators are constructed as closed units with fluid inlet and outlet ports providing external fluid connections to the inner ion exchange column.
U.S. Pat. No. 3,564,256 describes a radioisotope generator in which the ion exchange column is in a cylindrical holder which is located within two box-shaped elements that are in turn located within appropriate radiation shielding. The holder is closed by rubber plugs at both ends, and the box-shaped elements have passages opposite each of the rubber plugs in which respective needles are located. At the outermost ends of the needles quick-coupling members are provided to enable a syringe vessel containing a saline solution to be connected to one of the needles and to enable a collection vessel to be connected to the other of the two needles. This document acknowledges that as the two syringes form a closed system there is no need for air to be withdrawn or added.
U.S. Pat. No. 4,387,303 describes a radioisotope generator in which air is introduced to the eluate conduit via a branched pipe so that the hollow spike used to delivery the eluate to be collected has a single bore as the air is introduced into the fluid upstream.
U.S. Pat. No. 4,801,047 describes a dispensing device for a radioisotope generator in which the vial containing the saline solution that will be used to flush out the desired radioisotope from the ion exchange column, is mounted in a carrier that is moveable relative to the hollow needle used to pierce the seal of the vial and to extract the saline solution. The drawings of this document clearly illustrate two separate spaced apart hollow needles one to deliver air and one to collect fluid. The dispensing device is intended to penetrate an elastic stopper and so presents the problem that any rotational movement of the eluant container will result in tearing of the stopper which in turn destroys the aseptic environment through the uncontrolled introduction of air into the system. A similar dual needle system is illustrated in U.S. Pat. No. 5,109,160.
Although piercing devices are known that employ a single spike with two channels such as that illustrated in U.S. Pat. No. 4,211,588 such piercing devices have been restricted in their application in general to intravenous systems.